It didn't take long for the backlash to come. Just when we were getting somewhere.

For decades, centuries even, mental illness has been a great secret, a bit like homosexuality in the first half of the 20th century: something to carry around in secret, something dismal, shameful and bad. But now, suddenly, we're talking about it. A volley of personal memoirs from the famous and not so famous has begun to spread the message: it's not your fault, it can happen to anyone, it's nothing to be ashamed of. (I of course have an interest to declare, as my depression memoir was also published this year.)

But this candour, this desire to shed light on a dark and hugely costly affliction, is apparently not to everyone's taste. Some people have had enough of depression memoirs already. I have heard from people who argue that after years of near silence about depression, it's now hard to get people to shut up about it. India Knight speaks for that constituency in a weekend opinion piece in which she says that we just don't need to hear from famous people any more about their depression, that the subject is no longer taboo, that there is no stigma attached to depression any more and we should all move on.

She's wrong of course. Depression makes you feel alone, afraid, an outcast. Hearing that it is an illness that can affect anyone is enormously helpful. Learning that rich and starry people suffer too makes you feel less broken, less bereft. Understanding that it affects rich and poor, successful and not so successful, men and women, old and young also helps you to comprehend: this is a universal scourge. It picked you, you didn't pick it. You really are not to blame.

The idea that there is no longer any stigma is, if anything, even more egregious. Ask anyone with depression who has a job and they will likely tell you of a tortuous process of concealment and subterfuge. Ask anyone with depression who doesn't have a job and they will talk about an agonising dilemma in the hunt for work: to front up and risk not getting the job, or to lie and then risk being "outed" in future.

And that's just in the world of work. In our wider social circles, few people really want to come clean, particularly men. Of all the men I've spoken to about their "thing", very few have been happy to be named or identified. The current incidence of depression is thought to be around three women for every man. I have a strong suspicion that that imbalance is simply down to the fact that a great number of men are keeping their wretched conditions very well concealed.

Time to Change, the organisation that has spent years trying to challenge negative attitudes towards people with mental health problems, says that millions of people with depression still face stigma. Importantly, it adds that when celebrities speak out about their experiences, it helps ordinary people identify with it and makes it easier for them to face what they are going through.

The single biggest misunderstanding surrounding depression is that we've all been a bit depressed at one time or another, so what's the fuss all about? We haven't all had depression. It's around one in four or one in five. Depression is very different from feeling a bit down. It's not that Monday morning feeling, or returning from holiday to find the house has been burgled. It's not even the end of the affair, or the loss of a friend. It's far more all-consuming. We've all had a cold, but we haven't all had pneumonia.

Yes, we read a lot about depression at the moment. Yes, it might be irritating for those who don't really come across it in their lives to be constantly reminded of the agonies of the most miserable species on the planet. As one critic of my book, Underneath the Lemon Tree, wrote, with a wry observation that I still find amusing: "Far from being the illness that dare not speak its name, it is actually quite hard to get it to shut up." That may be true. But it's irrelevant. We don't want to shut up until everyone understands that this is not a lifestyle choice or a niche thing that happens to a few wretched people in our midst but a very real, ubiquitous, debilitating, paralysing, often lethal illness that we should address and treat, not punish and marginalise.